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#1
03-13-2014, 06:33 PM
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350 Block Chamfered?
I was scanning craigslist and I came across a 350 block out of a '68 Firebird, its a WC block. The tops of the cylinders are chamfered and I am wondering if that is also the case with the 350 in my '70 Lemans. I have been lead to believe the 350HO motors in 68-69 had the chamfered heads to allow the large valves.
Any info on this will be greatly appreciated.  
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1970 Lemans 350/ TH350 ProTouring Madness |
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#2
03-13-2014, 08:23 PM
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I can't answer your question but my 69 YD 400 also has chamfers in each cylinder. Originally had small valve heads, 2bbl, small cam, economy engine.
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1967 GTO, 432 (428+.030), 4-bolt mains, factory Nodular crank, scat rods, icon dished pistons, Lunati HR 243/251@.050, .618/.622 lift, Edelbrock 72cc round port heads, 10.5:1, offy 2-4 intake, Edelbrock 650cfm carbs, Super T10 trans (2.64 first), BOP 10 bolt w/ Eaton posi and 3.36 gears |
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#3
03-13-2014, 08:49 PM
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I just looked at pictures of my 1970 350 and it has them.
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#4
03-14-2014, 06:42 AM
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Those lifter bores look pretty rusty,I might pass on that block unless your gonna run some type of roller cam in it.
Lifter bores that have .003" more clearance than needed will never allow a new flat tappet cam and lifter to bed in right!
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#5
03-14-2014, 11:49 AM
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My 72 350 in my GP has the chamfered cylinders. Don't know how long Pontiac did that on the 350 blocks after 72.
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1971 GTO,72 400, stock bottom end, 670 heads, Lunati BMII cam, headers, iron intake Q-jet, four speed. Best 60 ft 1.806in 2004. Best 1/8th mile e.t. 8.46 with 3.55 open rear 85 Grand Prix, 70 400, casting 62 heads stock rebuild, Turbo 350 trans 78 800 cfm Q-jet modified as per Cliff Ruggles book. 87 F350 6.9 4 speed dually A poor man has poor ways. |
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#6
03-14-2014, 01:29 PM
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Thanks for the replies, knowing the 350 block in my car should have chamfered cylinders means I can go ahead with big valve heads like the '69 350HO had.
Quote:
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1970 Lemans 350/ TH350 ProTouring Madness |
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#7
03-14-2014, 02:26 PM
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Quote:
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1972 Pontiac Lemans 350 Qjet Summit 2800 |
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#8
03-14-2014, 07:50 PM
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I think all 68-72 350's have both sides notched even though only one year got 2.11/1.77 combo. Its likely inline with the 400's those years having 2.11/1.77 valves and if heads got accidently swapped it would still run but low compression. All D ports lost 1.77 exh after 72 so the exhaust side 350 notch went away too...
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63 Catalina coupe 467 cid budget drag car 11's 1/4 , 7.20 1/8th pump gas n/a 66 Star Chief Executive 57k mile 69 Le Mans 2 dr HT 350 85k mile 15 sec 1/4 69 Firebird 400 Burgandy/Black 70 Olds Rallye 350 F85 4 speed 3.91's 70 Olds Cutlass Cruiser Red Wagon 350 101k miles 15 sec 1/4 12 sec w 455 74 Cheyenne Super C10 LWB Gen 6 454 w ZZ502 cam 3.07gear 13.1 1/4, 8.3 1/8 2020 RAM 1500 SLT 4x4 5.7 A8 Hemi 2007 Hummer H3 3.7 liter turd 2019 Chevy Spark petrol car 38 mpg |
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#9
03-14-2014, 08:14 PM
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I tore down a 73 350.It had both side chamfered also.
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#10
03-14-2014, 08:59 PM
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326 and 350 blocks had chamfered cylinder bores.
 For some reason I didnt realize the 350 engines had the "transfer lug" on the rh side of the top of the bellhousing area like the 428/455s did though. Thanks for posting the pictures.
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#11
03-14-2014, 11:10 PM
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The bore chamfers on the small bore engines are'nt there to clear big valves or such,as at the lower lifts the factory used never gets the valves close enough to the bores to be a major concern interference wise,the chamfers are there to help band-aid flow into/outta the bore by unshoruding the valve "curtain" area somewhat.
Which 350's has them is hit or miss,I've seen them with one,both,none,you name it. But yeah,many have both. Bret P. |
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#12
03-15-2014, 08:31 AM
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Seems like most have the chamfers, but as Bret says it does not really help with valve clearance. You can safely run big valves with a factory cam like an 068 because they all have low lift. Clearance for aftermarket cams with higher lift seems to depend on the particular block and head combination. Based on my experience lifts above .450 are where you can get into trouble with most of the late 60's heads. Only way to know for sure is to fit the heads and check it.
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1969 Lemans vert, matador red, 462 CI, 3.07 12-bolt posi 1974 455 TA, admiralty blue/red interior HPP "cover car" - sold "The best way to show a car is to drive it" |
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